4 Channel DMX512 Driver for PIC16F1823

The original DMX512 driver project #800 is now redesigned to incorporate the optional address configuration switch on the main PCB.

The no-switches in-band DMX configuration feature is still retained

Double sided PCB has resulted in a more compact board size.

Firmware has been updated to run a latest generation enhanced midrange PIC16F1823 processor.

Description

This project is a 4 channel DMX512 driver board. It features four power MOSFETs that can be configured to operate in PWM mode or as on/off outputs. The driver can be configured to use any four consecutive addresses across the full 512 channel address range. It can drive LED arrays or low voltage lamps with either an 8 bit (256 step) PWM dimming signal or digital on/off mode under DMX control.

Outputs can drive LED modules, strips, lights or low voltage lamps up to 35 watts.

Two output modes:

8 bit resolution PWM mode with a PWM period of 5ms (200Hz).

digital on/off output.

Operating mode is individually configurable for each output

Operate as four independent outputs or Ganged operation where all four outputs are controlled from the base address DMX data channel

When no DMX data is received the driver can be configured to turn off all outputs, or leave them in their current state.

Configuration held in EEPROM so once configured can operate with no external switches or jumpers.

In keeping with the original 4-channel DMX driver project #800, the firmware supports a minimal external hardware design.

Although the new PCB805B has a configuration DIP switch on the board, the DMX base address and configuration modes are stored in the microcontrollers internal non-volatile EEPROM. Once settings have been made the firmware uses the saved settings from the EEPROM if no DIP switch is detected.

Additionally the original configuration via in-band DMX channel data is still supported. Fitting a single jumper puts the firmware into ‘in-band’ configuration mode. DMX data sent in the first four channels is saved to the EEPROM allowing the DMX base address and configuration word to be setup without the use of the external DIP switch.

Apart from resistor R13 all other resistors are 0.125 (1/8) watt parts. These a specified for physical space constraint reasons on the PCB.

The output driver MOSFETs Q1-Q4 are STP36NF06L or STP20NF06L. These are logic level devices designed to operate with a low gate drive voltage. If an alternative non-logic level part is substituted you may need to derate the maximum output current per channel

The PIC16F1823-I/P (IC1) requires programming with the DMX firmware. This part is only available from Picprojects as a pre-programmed and code protected part. (the firmware is not available to download)See Pre-Programmed PICs section of the on-line eShop

Construction notes:

Please read through this section at least once before starting assembly of the PCB

Assembly is straightforward. You will need previous experience soldering electronic components, a suitable soldering iron, hand tools and a multi-meter.

All photographs in the section link to a hi-res 1024×768 image for more detail.